Means for maintaining the focus of arc projectors



Aug. 28, 1923. r 1,466,419

P. R. BASSETT MEAN$ MAINTAINING THE FOCUS OF ARC PROJECT OHS Filed Oct. 15 1918 2 Sheets-Sheet 1 LV V/LVTOR M .sfolz m TTIOR/VL Y Aug. 28, 1923. 1,466,419

. P. R. BASSETT MEANS FOR MAINTAINING THE FOCUS OF ARC PROJECTORS Filed Oct. 15, 1913 2 sheets-Sheet 2 Patented Aug. 28, 1923.

UNITED STATES PATENT OFFICE.

PRESTON B; BABSETT, OI BROOKLYN, NEW YORK, ASSIGNOR TO THE SPERBY GYBO- SCOPE COMPANY, 01' BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK.

KEANE FOB MAINTAINING TEE FOCUS OF ARC PBOJECTORS.

Application filed October 15, 1918. Serial No. 258,255.

To all whom it may concern:

- Be it known that PRns'roN' R. BASSE'I'I, citizen of the United States, residing at 1716 Newkirk Ave, Brooklyn, in the county of Kings and State of New York, has invented certain new and useful Improvements in Means for Maintaining the Focus of Arc Projectors, of which the following is a specification.

This invention relates to are lights; particularlyas used in searchlights, and more specifically to a method and means for automatically maintaining the light source, which is located in the crater formed in the end of the; positive electrode, in a predetermined position, .so as to kee the said source the proper distance from t e reflector to maintain the desired projection of. the

light rays. In high intensity flaming arc lights, for use with which my invention is particularly adapted as illustrated by the flame structure in' Figures 1, 4 and 5, the source of light, instead of being in the flame of the arc, is concentrated in'the crater of the positive electrode, and this invention is concerned simply with positioning the light source at a definite distance from the reflector, the'length of the are being regulated by other means.

The most successful systems now used for this purpose com rise thermostatic devices which involve elicate and complicated mechanism requiring frequent adjustments. WVhile some of these systems function with a high degree of accuracy under favorable conditions, they are subject to inaccuracies under unfavorable conditions, such as heavy jars or shocks. 1

The object of this invention is to provide a. system whereby the position of thelight source may be controlled with'great accuracy under all conditions, and wherein the mechanism is simple, hardy, readily adjustable and inexpensive to manufacture.

Referring to the drawings wherein I have shown what I now consider to bethe preferred form of my invention:

Fig. 1 is a side elevation partly in section of a searchlight lamp showing the embodiment of my invention.

Fig. 2 is a sectional side elevation of th positive electrode head.

Fig. 3 is a section taken on line 3-3,

Fig. 2.

F 4 is a wiring diagram.

Fig. 5 is a wiring diagram, showing a modification.

In Fig. 1 of the drawings, 1 is a fra entary representation of a Searchlight rum, below which depends a control box compar'tment 2 integral therewith. Within said compartment is shown the control box 3 of the lamp, from the top of which the negative and positive electrode holders 4 and 5 proect upwardly into the drum. The said olders may comprise standards 10 and 11, having heads 6 and 7 fixed on the tops thereof. The negative electrode 8 is shown within the head 6 and is adapted to be fed therethrough toward'the positive electrode, while the positive electrode9 is shown within the head 7,' and may be rotated therein and fed therethrou h.

The mechanism or feeding the negative electrode through its holder may be the same as that shown and described in the copending application of Elmer A. Sperry for feeding mechanism for searchli hts, which on December 14, 1920, matured into Patent No. 1,362,575 and is therefore not shown here; it being suflicient to state that'the end 8' of the negative electrode is adapted to be automatically, maintained a predetermined distance from the crater in the end 9 of the positive electrode. The said end 9' on the other hand, being placed along the axis of a parabolic reflector orprojector 12 (see Fig. 4:) should be maintained at substantially a fixed distance from said projector in order to obtain the desired projection of the light rays 13. Also the positive electrode is preferably rotated while the light is burning so that the end 9' will burn off evenly and a symmetric crater 14 will be formed so as to confine the light source which is mostly within the crater, to as small an area as possible; it being recognized that the point source is the most eflicient for searchlights.

Numerous methods ma be employed for rotating the electrode. or this purpose I have shown the electrode 9 as gripped between two-rollers 15 and 16 (Figs. 2 and 3) mounted on brackets 17 and 18 on crown' gear 19 mounted for rotation on annular member v20 which is integral with the head 7. One of said brackets may be hingedly mounted on the said crown gear as at 18' and a spring 21 may be attached to projections 22 and 23 on said brackets for pressing the rollers tightly against the electrode.

Within the control box 3 is shown an electric motor 34 on the shalt 35 of which are provided worm teeth meshing with worm gear 37 on shaft 38. Ur. the top of shaft 38 is fixed gear 39 adapted to turn gear through an idler 41. Gear 40 is hxed on shaft 42, at the top of which, within the head 7 is also fixed bevel 4S meshing with the crown gear 19. Motor. 34 is adapted to rotate constantly during the operation of the lamp, so that the electrode will rotate continuously.

Fixed upon the same shafts 24 and 25 with rollers 15 and 16 are a pair of intermeshing gears 26 and 27. Also meshing with gear 28 is a pinion 28 on the same shaft 29 with a gear 30 which in turn meshes with pinion 31. Fixed on the outer end of the same shaft 32 with pinion 31 is a star wheel 33. It will readily be seen that rotation of said star wheel 33 will effect the rotation of rollers, 15 and 16 through the said chain of gears. so that the electrode 9 will be-moved longitudinally.

As crown gear 19 rotates. star wheel is obviously carried on a circular path as indicated by dotted lines 44 within the walls of head 7. Lying adjacent and below said path is shown an actuating rod 45 reaching down into the control box 3, where it is attached to a lever 46 which is pivoted at 47 on bracket 48. A magnet 49 adjacent one end of lever 46 may be employed for lilting said lever to raise rod 45. This will place the rod in the path of star wheel 33 so that one of its points will engage the rod during each revolution of the crown gear 19 and cause said star wheel to revolve slightly on its own axis, and thus effect the aforementioned longitudinal movement of electrode 9. A spring 50 secured to lever 46 and to an adjustable thumb screw 51 may, serve to normally hold rod 45 out of the path 44 of the star wheel. Adjustments of the tension of spring 50 may be made through thumb screw 51 so as to vary the strength necessary in magnet 49 to tilt lever 46.

To effect the energization of magnet 49, I desire to place the same in circuit with an additional electrode located adjacent the are for closing a circuit through said magnetwhen the position of the are changes.

While such third electrode may be placed in any suitable position with respect to said arc, have represented it at 52 below the are which is represented at 53. As shown, the electrode 52 is so positioned that as the positive electrode burns oil? and its end 9' recedes toward the holder 7, the lower portion or hump 54 of the arc will draw more closely to the end of electrode 52.

esa-11o In the wiring diagram shown in Fig. 4, it will be seen that if the are 53 touches electrode 52 a circuit will exist running from the source of power represented by a generator 55, through wires 56, 51'. coil 49, wire 58 electrode 52, through are 5;; to electrode 9 and back through line 59. It is not essential, however, that the flaming portion of the arc shall actually touch electrode 52 to close said circuit, since a considerable stray voltage so to speak or conducting gas normally surrounds the arc. The value of this gas as a conductor varies of course with the distance from the flame of the arc. The electrode as located in the drawings is constantly in engagement with the said gas, so that a weak current may always be passing through magnet if). This current. when the end 9' of the positive electrode is in the proper place, may not be strong enough to tilt lever 413. but as the are draws closer to said electrode the current will increase to a strength su'flicicnt to tilt said lever. The tension of spring 50 may be adjusted so that said tilting will take place at the desired time.

lVhile the system of control represented in Fig. 4 has been found sufficiently sensitive to keep the light source very close to a fixed position, I have shown a slightly modified system in Fig. 5, which is adapted to re spond with a greater degicc of sensitivencss, and which may be employed if desired In this form the current passing through electrode 52 is required to do much less work than in the form shown in Fig. 4. In this form, instead of requiring said circuit to lift rod 45, it is simply required by energizing a coil 49 to trip a lever 61 to actuate contact 62, thereby closing a strong circuit through magnet 49 to'efl'ect the feeding of electrode 9. Adjustments of the strength required to tilt lever 61 may be made through adjusting screw 51 and spring 50. One advantage of this arrangement is that. since a much weaker current is required to tilt lever 61, electrode 52 may be placed a reater distance from the arc and thus be ess apt to become destroyed by the intense heat.

Other features which are designed to aid in preserving electrode 52 from consumption or too rapid consumption by the are or the heat from the arc, are the composition and the shape of the electrode. \Vhile it ma y be composed of carbon I prefer to use a metal having suitable current conducting properties, rapid heat. conducting properties, and a high melting l'QlllPPlfiilll't. To this end I prefer to use copper which may be covered as by calorizing with aluminum or electroplating with silver or other substance capable of preventing or retarding oxidation. In shape, the electrode end 65 which is the contact making end may be small enough to be confined to a small area, and may spread out to a larger body portion 65. Thus the heat received at the end may spread rapidly away therefrom.

en consumption of the end 65 does take place, however, the tension on spring 0r spring 50 may be lessened so that the tilting of levers 46 or 61 may still take place at the correct time to maintain the light source in its proper position. Compensation for consumption of the end 65 and also adjustment of the normal position of the posi- -tive crater with respect tothe' projector may be made by moving electrode 52 toward the are. For this purpose said electrode is shown as mounted in a holder 66 which is slidably mounted on a bracket 67 secured to standard 11. An arm 68 on holder 66 is attached at its lower'end to a rod 69 reaching down into the control box 3. A spring 70 butting against a collar 71 fixed on rod 69 and against insulation 72 through which the rod passes into the control box may serve to tend to move rod 69 upwardly and thus move electrode 52 toward the arc, while an adjustable; nut 3 screwed upon the end '74 of rod 69 and against the lowenpart of insulation 72 may serve to hold said rod against the tension of said spring. Thus the turning of nut 73 may serve to adjust electrode 52 with respect to the are.

The electrical connection between electrode 52 and magnet 49 may be eflected by insulating bracket 67 from standard 11 by means of insulation 75, and connecting the lower end 74 of rod 69 to magnet 49 by means of conductor 76.

If it becomes desirable to feed the positi e electrode manually for any reason, this may be effected by the pulling of a rod 80 attached-to a bell crank lever 81 pivoted at 82 on bracket 48. Said bell crank lever is normally held in inoperative position by a spring 83 attached thereto and to the end of the control box 3 at 84. Upon pulling rod 80 the end 85 of bell crank lever 81 will raise lever 46 and effect the said feeding.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention, to-- gether with the apparatus, which I now consider to represent the best embodiment thereof, but I desire to have it understood that theapparatns shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described; some of these may be altered and others omitted without interfering with the more general results outlined,.and the invention extends to such use. 1

Having-described myfinvention, what I claim and desire to secureby Letters Patent 1s:

1. In an arc lamp, a pair of electrodes adapted to produce an are. means for feeding one of said electrodes independently of the other, a third electrode adjacent the are tips of said electrodes, and means controlled by the current passing through said third electrode for controlling said feeding means.

2. In an arc lamp, a pair of electrodes adapted to produce an arc, means for feeding one of said electrodes independently of the other, electro-magnet-ic means in circuit with one of said electrodes for bringing into operation said feeding means and an additionaLelectrode adjacent the arcing endsof said first mentioned electrodes and in circuit with said elcctromagnetic means. said additional electrode being adapted to engage the arc to close a circuit through said electro magnetic means.

3. In an arc lamp, the combination with a pair of electrode holders, of mechanism for feeding an electrode thru one of said holders, means for actuating said mechanism, and an additional electrode on said holder and adjacent the are, said additional electrode being in circuit with a source of energy and with said actuating means to energize the same in res )onse to the position of one ofthe electro es.

4. In alight projecting device, a projector, a pair of electrodes, means for positioning one of said electrodes with respect to the projector, electro-lesponsive means for positioning the other electrode with respect to the first electrode, and a third electrode adjacent the arc and in circuit with said first mentioned means for actuating the same.

5. In an are light, a projector, a positive and a negative electrode adapted to produce an arc,.the crater of the positive electrode containing the principal light source, an electric conductor adjacent the arcing face of the positive electrode, and means in circuit with said conductor and actuated by stray current, from the are when said electrode burns back for feeding the same forwardly to maintain said light source in a predetermined position with respect to said projector.

6. In anarc light, a positive and a negative electrode, the crater of the positive electrode containing the principal light source, means for feeding the positive electrode, an electric conductor adjacent the arc, and means in circuit with said conductor and operated by variations in the passage of current therethrough, due to variations in the electric field adjacent said conductor caused by the are flames for controlling said feedin means.

In an arc 1ight,a pair of electrodes adapted to produce an arc, means for feeding one of said electrodes, an electric conductor ad acent the are, and means in circuit with said conductor and operated by variations in the passage of current therethrough, due to variations in the electric field adjacent said conductor caused by the arc flames for controlling said feeding means, said con- (luctor being so positioned relative to said electrodes and said are that the means for controlling the feeding means is non-responsive to the burning away of one of said electrodes.

8. A feeding means for electrodes of arc lights having spaced electrodes adapted to be fed toward each other comprising power driven mechanism, variable means for caus- Eng feeding of an electrode by said mechanism, and electrical means responsive to the electronic field surrounding the arc flame adjacent said electrode for governing said variable means.

9. In an arc lamp, the combination with the electrode holders,\ of means for feeding an electrode associated therewith, separate means for feeding the other electrode and means responsive to the proximity of the arc flame for controlling one of said feeding means comprising a conductor adjacent the are and connected to one side of the arc supply and electro-magnetic means in circuit with said conductor and said are supply.

10. In an arc lamp, the combination with the electrode holders, of means for feeding an electrode associated therewith, means responsive to the electrical properties of the are flame for controlling said feeding means comprising a conductor adjacent the are, electro-xnagnetic means in circuit therewith, and a contact controlled by said electro-magnetic means and in circuit with said feeding means for controllingthe latter.

11. In an arc lamp, a pair of electrodes adapted to produce an are, means for feeding one of said electrodes, a third electrode formed of a block of copper, positioned with the greater portion thereof lying away from the arc flame, and means controlled by the relative position of said third electrode and are for controllin said feeding means.

12. In an arc amp, a pair of electrodes adapted to produce an are, means for feedin one of said electrodes, a third electrode formedof a block of copper of tapering shape with the thicker portions thereof lying away from the are, and means controlled by the relative position of said third electrode and are for controlling said feeding means.

13. In an are light, in which the principal light source lies adjacent one electrode, an electric conductor adjacent the tip of said electrode comprising a calorized copper block, and feeding means for said electrode controlled by current passing through said conductor.

In testimony whereof I have aflixed my signature.

PRESTON R. BASSETT. 

